The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Homogenous charge compression ignition (HCCI) engines combust an air/fuel mixture within cylinders to produce drive torque. HCCI engines may combust the air/fuel mixture in different combustion modes. In an HCCI combustion mode, the air/fuel mixture is automatically ignited when compressed by the pistons. In a spark ignition (SI) combustion mode, the air/fuel mixture is ignited by spark plugs. The HCCI combustion mode may improve efficiency and fuel economy of the engine over the SI combustion mode.
Engine control systems have been developed to operate a gasoline engine in the HCCI combustion mode and the SI combustion mode. Operation using the HCCI combustion mode has been limited to an HCCI operating zone. The HCCI operating zone may limit operation of HCCI combustion based on engine speed, mass airflow, or fueling rate.